Rear wheel alignment? If not try putting your wallet in the other pocket and see if it steers that way Jim
Yep, pull axle back on the left side, forward on the right. Just a tad.Cheers
Could be a slight twist in the frame. Has it ever pulled a chair? Can you feel it when riding normally as in with hands on the bars? The rear sprocket needs to align with the run of the chain or it will wear on the side.